JP2000345926A - Exhaust gas reflux device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow an EGR device to function efficiently even at the cold time of an internal combustion engine by forming EGR gas passages almost parallel with water jackets provided inside a cylinder head of the internal combustion engine, and introducing EGR gas into an intake passage via these EGR gas passages. SOLUTION: A cylinder head 1 fitted to the upper part of a cylinder block of an internal combustion engine is provided inside thereof with three water jackets 4a-4c arranged at the upper part of a combustion chamber and on the lateral sides of the combustion chamber in a cylinder row direction and connected to a water pump 2, and EGR gas passages 5a, 5b into which EGR gas are introduced, are arranged at the side of the water jackets 4b, 4c. In this case, the EGR gas passages 5a, 5b are provided almost parallel with the water jackets 4b, 4c, outside of the water jackets 4b, 4c arranged inside the cylinder head 1 almost horizontally in the cylinder row direction and below intake and exhaust ports on the outside of the combustion chamber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an exhaust gas recirculation device (hereinafter, EGR device) for an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, in order to reduce nitrogen oxides contained in exhaust gas in a medium load region of an internal combustion engine, a part of the exhaust gas is returned to an intake passage and the temperature of the combustion gas in a combustion chamber is reduced. There is known an EGR device that suppresses the generation of nitrogen oxides by lowering it (see Japanese Patent Application Laid-Open No. 5-102213).

FIG. 8 shows a typical EGR device.

[0004] An intake manifold 8 for guiding air introduced from an intake duct into a combustion chamber and an exhaust manifold 9 for discharging exhaust gas from the combustion chamber are connected to the cylinder head 1.

An intake manifold 8 and an exhaust manifold 9
Is connected by an EGR passage 21, and a control valve 7 for controlling the amount of exhaust gas circulated in accordance with the operating conditions is provided in the middle of the EGR passage 21.

[0006]

However, when the internal combustion engine is cold, the fuel is insufficiently vaporized or atomized, and the combustion tends to be unstable. If EGR is performed in this state, the combustion temperature decreases, and the combustion further proceeds. Has become unstable and the amount of hydrocarbons has increased rapidly.

The present invention has been made in view of the above problems, and has as its object to make the EGR device function efficiently even when the internal combustion engine is cold.

[0008]

According to a first aspect of the present invention, there is provided an exhaust gas recirculation device for introducing a part of exhaust gas of an internal combustion engine from an exhaust passage into an intake passage, provided in a cylinder head of the internal combustion engine. And a water jacket extending in communication with each other in the cylinder row direction and cooling water flowing through the cooling chamber, and an E disposed in the cylinder head substantially parallel to the water jacket.
A GR gas passage is provided, and EGR gas is introduced into the intake passage via the EGR gas passage.

According to a second aspect of the present invention, in the first aspect, the cylinder head has an ignition plug arranged offset to the exhaust side, and the EGR gas passage arranged only to the intake side.

[0010] In a third aspect based on the first aspect, the cylinder head has an ignition plug offset to the intake side and the EGR gas passage arranged only to the exhaust side.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the EG passing through the EGR gas passage is provided.
The flow direction of the R gas is the same as the flow direction of the cooling water in the water jacket.

According to a fifth aspect of the present invention, in any one of the first to third aspects, the internal combustion engine is a vertically mounted internal combustion engine having a cylinder array arranged in a vehicle front-rear direction. The cooling water in the water jacket flows from the rear side to the front side while the water is passed from the front side to the rear side of the internal combustion engine cooled by the wind.

According to a sixth aspect of the present invention, in any one of the first to fifth aspects, a catalyst is provided in the exhaust passage, and the EG is provided.
The outlet side of the R gas passage is connected to the intake passage and the exhaust passage downstream of the catalyst, and a switching means is provided at a branch portion between the intake passage and the exhaust passage so that the EG discharged from the EGR gas passage is provided.
The flow of the R gas can be switched between the intake passage and the exhaust passage by the switching means.

In a seventh aspect based on the sixth aspect, a portion of the EGR gas discharged from the EGR gas passage by the EGR gas switching means is introduced into the exhaust passage when the internal combustion engine is cold. did.

According to an eighth aspect of the present invention, in any one of the first to seventh aspects, a thermostat is provided in a cooling water passage through which the cooling water passes, and the thermostat controls a flow of the cooling water according to the temperature of the cooling water. The set temperature of the thermostat is set to be lower by the amount by which the cylinder head is warmed by the EGR gas.

[0016]

According to the first aspect of the present invention, the EGR gas passage through which the EGR gas passes is provided substantially in parallel with the water jacket extending in the cylinder row direction in the cylinder head, and the EGR gas supplied from the exhaust passage to the intake passage is provided. Is passed through the inside of the cylinder head, so that when the engine is cold, the temperature of the cylinder head is quickly raised by introducing EGR gas into the cylinder head to promote gasification and atomization of fuel. By raising the combustion chamber wall temperature, the combustion can be stabilized, and the generation of hydrocarbons can be suppressed.

Therefore, the EGR can be started early after the engine is started, and the generation of NOx can be effectively suppressed.

In the second aspect of the present invention, since the cylinder head has the ignition plug offset to the exhaust side and the EGR gas passage only to the intake side, high-temperature EGR gas is introduced into the intake side EGR gas passage. Thus, the temperature of the cylinder head on the intake side can be increased, and the temperature distribution around the combustion chamber can be made substantially uniform.

In the third aspect of the invention, the cylinder head has the spark plug offsetly arranged on the intake side and the EGR gas passage arranged only on the exhaust side. Therefore, high-temperature EGR gas is introduced into the exhaust side EGR gas passage. Thus, the temperature of the cylinder head on the exhaust side can be increased, and the temperature distribution around the combustion chamber can be made substantially uniform.

In the fourth aspect of the present invention, since the flow direction of the EGR gas passing through the EGR gas passage is the same as the flow direction of the cooling water in the water jacket, the cylinder head becomes closer to the upstream cylinder side where the cooling water is introduced. Although the temperature tends to decrease, by introducing the EGR gas from the same direction, the upstream cylinder is heated by the high-temperature EGR gas, and the transferred coolant is transferred and circulated in the engine. Thereby, the temperature distribution of the cooling water can be made uniform, and the variation in combustion between the cylinders can be suppressed.

According to a fifth aspect of the present invention, the internal combustion engine is a vertically installed internal combustion engine having a cylinder array arranged in a vehicle front-rear direction. While passing the cooling water in the water jacket from the rear side to the front side,
Since the flow direction of the EGR gas passing through the GR gas passage is different from the flow direction of the cooling water, when the front side of the engine is cooled by the traveling wind, the cooling water is introduced from the rear side, and the EGR gas is supplied to the front side. , The front side of the engine is warmed, the temperature drop due to the traveling wind is canceled, and the temperature inside the engine can be kept uniform.

In the sixth and seventh inventions, a catalyst is provided in the exhaust passage, and the outlet side of the EGR gas passage is connected to an intake passage and an exhaust passage downstream of the catalyst. A switching means is provided in the section so that the flow of the EGR gas discharged from the EGR gas passage can be switched between the intake passage and the exhaust passage by the switching means. Without having to warm up the cylinder head. In addition, since the EGR gas is passed through the cylinder head even after the engine warm-up is completed, the temperature of the EGR gas can be reduced, and high-rate EGR can be performed.

In the eighth invention, a thermostat is provided in the cooling water passage through which the cooling water passes, and the thermostat controls the flow of the cooling water in accordance with the temperature of the cooling water. Temperature is set low, so that E
When the GR is stopped, the amount of cooling water for cooling the engine can be relatively increased, so that the cooling performance of the engine increases,
Performance such as knocking resistance is improved.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to the accompanying drawings.

First, FIGS. 1 and 2 will be described. Reference numeral 1 denotes a cylinder head mounted on an upper portion of a cylinder block (not shown), and a water pump 2 for circulating cooling water is disposed on a side surface of the cylinder head 1. Three water jackets 4 a, 4 b, 4 c are provided in the cylinder head 1 in the cylinder row direction, respectively, at the upper part of the combustion chamber, at the left and right sides of the combustion chamber, and connected to the water pump 2.

One of the radiators 6 for introducing cooling water into the water pump 2 is connected to the water jackets 4a, 4b, 4c in the cylinder head via the thermostat 3.
Connect to

Further, EGR gas passages 5a, into which EGR gas is introduced, are provided beside the water jackets 4b, 4c.
The EGR gas passages 5a and 5b will be described later in detail.

The cooling water that has cooled the cylinder head 1 by the water jackets 4a, 4b, 4c provided in the cylinder head 1 passes through the thermostat 3 from the cylinder head 1, checks the cooling water temperature, and is sent to the radiator 6. When the temperature is equal to or higher than the predetermined temperature, an electric fan (not shown) operates to lower the cooling water temperature. When the predetermined temperature is not reached, the electric fan does not operate.

Next, the cooling water is sent from the radiator 6 to the water pump 2, and from the water pump 2, the water jackets 4 a, 4 b, 4
Cooling water is sent to c.

The water jackets 4a, 4b, 4c provided in the cylinder head 1 are provided around the combustion chambers of each cylinder so as to avoid the intake port and the exhaust port, and these are communicated with each other between the cylinders. One of the three water jackets 4a, 4b, and 4c is provided in the cylinder row direction. 1.

The shape of the combustion chamber of the first embodiment is symmetrical with respect to the spark plug.

EGR gas passage 5 into which EGR gas is introduced
a and 5b are arranged substantially horizontally in the cylinder row inside the cylinder head 1 and substantially parallel to the water jackets 4b and 4c outside the water jackets 4b and 4c arranged outside the combustion chamber and below the intake and exhaust ports. EGR gas is introduced from the exhaust manifold 9 to the upstream side through an exhaust-side EGR pipe 5c. A control valve 7 for controlling the recirculation amount of the EGR gas is provided in the middle of the exhaust-side EGR pipe 5c. EGR gas passage 5a,
The EGR gas recirculating to the 5b is introduced into the cylinder head from the # 1 cylinder side into the EGR gas passages 5a and 5b in the same manner as the cooling water.

The downstream sides of the EGR gas passages 5a and 5b merge with each other, and the EGR gas is introduced into the intake manifold 8 through the intake side EGR pipe 5d and functions as an EGR device.

Although the EGR gas passages 5a and 5b are provided in the cylinder head, the EGR gas passages 5a and 5b may be configured to be attached to the side surface of the cylinder head 1 by a separate component.

Next, the operation of the present invention will be described.

EGR gas passages 5a and 5b for introducing EGR gas recirculated from the exhaust manifold 6 are provided in the cylinder head 1 substantially in parallel with the water jacket 4 in the cylinder head 1, and the exhaust gas is supplied to the cylinder similarly to the cooling water. Since the gas flows in the EGR gas passages 5a and 5b in the row direction, even when the engine is cold, heat exchange between the EGR gas having a higher temperature than the cooling water and the high flow rate and the cylinder head 1 is performed. And the cylinder head 1
Is quickly heated, and the vaporization of the fuel in the combustion chamber is promoted. Therefore, the combustion state is improved, and the exhaust gas, in particular, the hydrocarbon component in the exhaust gas can be reduced.

The EGR gas passages 5a and 5b are provided substantially parallel to the water jackets 4b and 4c, and the flow direction of the EGR gas is introduced from the upstream cylinder side (# 1 cylinder) into which the cooling water flows. The coolant is warmed by heat conduction through the cylinder head 1, and the coolant circulates through the engine, so that the coolant temperature between the cylinders can be made substantially uniform.

That is, the # 1 cylinder located on the upstream side where the cooling water from the radiator 6 is introduced and the # 1 cylinder located on the most downstream side
In four cylinders, there is a difference in cooling water temperature. Since the cooling water that has reached the downstream # 4 cylinder has already been transferred to the cylinders # 1 to # 3, the cooling water temperature becomes higher toward the downstream side.

However, in the present invention, the EGR gas is supplied substantially parallel to the water jackets 4b and 4c and
By flowing the gas from the # 1 cylinder side into which the cooling water flows, before the EGR gas is introduced, the temperature of the cylinder head 1 and the cooling water temperature become higher toward the # 4 cylinder side as shown in FIG. 3A. However, due to the introduction of EGR gas, the amount of heat of the EGR gas is obtained on the # 1 cylinder side where the temperature difference from the EGR gas temperature on the upstream side is larger, and the temperature of the cylinder head 1 and its cooling water is C in FIG. As shown in FIG.

Therefore, by equalizing the temperature distribution of the cylinder head 1, variation in combustion between the cylinders can be suppressed, and a favorable combustion state can be maintained.

In the figure, B shows the temperature distribution of the EGR gas introduced into the cylinder head 1.

Further, the set temperature of the thermostat is set to EGR.
When the EGR is stopped when the engine is under a high load,
Since the amount of cooling water for cooling the engine can be relatively increased, the cooling performance of the engine is improved, and the performance such as knock resistance is improved.

FIG. 4 shows a second embodiment.

This is different from the first embodiment in that a first catalyst 10 is provided on the downstream side of the exhaust manifold 9 and a second catalyst 11 is further provided on the downstream side thereof. An EGR pipe 5e is connected to an exhaust duct between the first catalyst 10 and the second catalyst 11, so that the flow of EGR gas can be switched between the EGR pipe 5e and the intake manifold 8.

A controller 19 is provided for controlling the opening and closing of the control valve 7 and the three-way valve 12 according to the operating state of the engine. For this reason, the controller 19 includes a temperature sensor 13 for detecting the temperature Th of the cylinder head 1 on the cylinder head 1, a sensor 14 for detecting the open / close state of the control valve 7 for the control valve 7, and a three-way valve 12 for the three-way valve 12. Output signals are sent from a sensor 15 for detecting the open / closed state of the valve 12, a sensor 16 for detecting the engine speed Ne, and a detection device 17 for detecting the load T of the engine. The opening and closing of the three-way valve 12 is controlled to control the flow of the EGR gas.

The temperature of the cooling water may be detected instead of the temperature of the cylinder head 1.

FIG. 5 is a flowchart showing the contents controlled by the controller 19, based on which the control contents will be described in detail.

The control content is the state of the engine, that is, when the engine is cold.
The control content differs depending on the medium load and high load.
After describing the overall control flow, each will be described sequentially.

First, in step S 1, the temperature of the cylinder head 1 is read from the temperature sensor 13.

Subsequently, in step S2, the open / close state of the three-way valve 12 is detected using the sensor 15. When the open / close state is undefined, the three-way valve 12 is switched so that the EGR gas flows to the exhaust duct side.

In step S3, the detected temperature Th of the cylinder head 1 is compared with a threshold value Ta. If the detected temperature Th is lower than the threshold value Ta, the process proceeds to step S4. If the detected temperature Th is higher, the process proceeds to step S4. Proceed to step S5.

In step S4, the three-way valve 12 is switched so that the EGR gas flows toward the exhaust duct, and the controller 19 controls the control valve 7 and the three-way valve 12 so that the control valve 7 is fully opened.

By performing such control, when the temperature of the cylinder head 1 is low, EGR gas is introduced into the head 1 to warm the head 1, and the combustion state is reduced by not introducing EGR gas into the intake air. Can be improved.

The temperature Th of the cylinder head 1 is equal to the threshold value T.
If it is higher than a, the process proceeds to step S5, and step S5
Then, the open / close state of the control valve 7 is detected by the sensor 14. When the control valve 7 is open, the process proceeds to step S7. This is a process for not closing the control valve 7 when entering this routine during the EGR control.

In step S6, the control valve 7 is initialized and closed. This is a process for preventing the EGR gas from flowing rapidly when the three-way valve 12 is operated, thereby preventing the stability of the engine from deteriorating.

In step S7, the three-way valve 12 is switched so that the EGR gas flows toward the intake manifold 8.

In the following step S8, the rotation speed sensor 16
And the load detecting means 17 to detect the engine speed Ne and the engine load T.
It is determined whether or not to perform R. If EGR is to be performed, the process proceeds to step S10, and the opening of the control valve 7 is determined by the controller 19 based on the EGR map based on the engine speed and the engine load.
Is controlled to obtain an EGR amount corresponding to the operating state.

When the condition for performing EGR is not satisfied, the process proceeds to step S11, the control valve 7 is closed, and the control is terminated.

The flow of control when the engine is cold will be described based on the above control contents.

Since the engine is cold at the time of cold, the three-way valve 12 is switched so that the EGR gas flows to the exhaust duct side, and the control valve 7 is fully opened. Thus, the EGR gas is introduced into the EGR gas passages 5a and 5b by the pressure difference before and after the first catalyst 10 without introducing the EGR gas into the intake manifold 8. For this reason, the warming-up of the cylinder head 1 is promoted, the fuel vaporization is promoted, and the fuel wall flow is reduced, so that the combustion state is improved and the amount of hydrocarbons can be reduced. In this case, EGR
The gas will be introduced downstream of the first catalyst 10,
The exhaust gas is discharged after the second catalyst 11 purifies the exhaust gas.

In the low-load and medium-load state where the warm-up is completed,
The three-way valve 12 is switched so that the EGR gas flows to the intake manifold side, the opening of the control valve 7 is adjusted according to the engine speed Ne and the engine load T, and the optimum EGR is performed.
Reduce NOx.

When the engine has a high load, EGR is not performed.
By closing the control valve 7, the E
The flow of the EGR gas into the GR gas passage 5 is shut off. At this time, the set temperature of the thermostat 3 is set lower than usual in consideration of the amount of heating of the cylinder head 1 by the EGR gas, so that the cooling water amount increases. And cylinder head 1
Can be suppressed lower than usual, so that knocking resistance is improved.

FIGS. 6 and 7 show the second and third embodiments, in which the spark plugs 20 arranged in the combustion chambers 21 and 22 are offset in the left-right direction of the cylinder head. .

In the case of the combustion chamber 21 shown in FIG. 6, since the spark plug 20 is offset to the exhaust side, it is easy to secure a space for the water jacket 23 on the intake side.
Although the intake side is easily cooled and a temperature difference occurs between the intake side and the exhaust side, the temperature difference can be eliminated by providing the EGR gas passage 25 on the intake side.

In the case of the combustion chamber 22 shown in FIG. 7, since the spark plug 20 is offset to the intake side, the exhaust side is easily cooled, and a temperature difference is generated between the exhaust side and the intake side, contrary to FIG. The temperature difference can be eliminated by providing the EGR gas passage 26 on the exhaust side.

Furthermore, the flow direction of the cooling water in the cylinder head 1 and the flow direction of the EGR gas have been described as the same direction. However, the present invention is not limited to this.
The flow direction of the GR gas may be reversed. For example, when the engine is placed vertically on the vehicle, the traveling wind only hits the front of the engine, and only the front of the engine is cooled, and the temperature distribution of the entire engine becomes uneven. By introducing EGR gas from the front side of the engine and introducing cooling water from the rear side in order to eliminate such temperature non-uniformity, it is possible to warm the front of the engine and eliminate non-uniform temperature in the engine. .

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a flow of an EGR gas.

FIG. 3 is a diagram showing a relationship between a cylinder position and a cylinder head temperature.

FIG. 4 is an explanatory diagram showing a flow of an EGR gas according to a second embodiment.

FIG. 5 is a flowchart for explaining control contents.

FIG. 6 is a sectional view showing another combustion chamber shape.

FIG. 7 is a sectional view showing another combustion chamber shape.

FIG. 8 is an explanatory diagram showing a flow of an EGR gas in a conventional example.

[Explanation of symbols]

 Reference Signs List 1 cylinder head 2 water pump 3 thermostat 4a water jacket 4b water jacket 4c water jacket 5a EGR gas passage 5b EGR gas passage 5c EGR gas passage 5d EGR gas passage 5e EGR gas passage 6 radiator 7 control valve 8 intake manifold 9 exhaust manifold 1 catalyst 11 second catalyst 12 three-way valve

Claims (8)

[Claims] An exhaust gas recirculation device for introducing a part of exhaust gas of an internal combustion engine from an exhaust passage into an intake passage is provided in a cylinder head of the internal combustion engine, through which cooling water is circulated to form a combustion chamber. A water jacket that cools the surroundings and extends in communication with each other in the cylinder row direction; and an EGR gas passage disposed in the cylinder head substantially parallel to the water jacket, and via the EGR gas passage. Exhaust gas recirculation device for an internal combustion engine, wherein an EGR gas is introduced into an intake passage. 2. An exhaust gas recirculation system for an internal combustion engine according to claim 1, wherein said cylinder head has an ignition plug offsetly disposed on an exhaust side and said EGR gas passage disposed only on an intake side. 3. The exhaust gas recirculation system for an internal combustion engine according to claim 1, wherein the cylinder head has an ignition plug offset to the intake side and the EGR gas passage disposed only to the exhaust side. 4. The internal combustion engine according to claim 1, wherein the flow direction of the EGR gas passing through the EGR gas passage is the same as the flow direction of the cooling water in the water jacket. Exhaust gas recirculation device. 5. The internal combustion engine according to claim 1, wherein the internal combustion engine is a vertically disposed internal combustion engine having a cylinder row arranged in a front-rear direction of the vehicle. The exhaust gas recirculation device for an internal combustion engine according to any one of claims 1 to 3, wherein the flow direction of the cooling water in the water jacket is from a rear side to a front side. 6. A catalyst is provided in the exhaust passage, an outlet side of the EGR gas passage is connected to an intake passage and an exhaust passage downstream of the catalyst, and switching means is provided at a branch portion between the intake passage and the exhaust passage. The exhaust gas of an internal combustion engine according to any one of claims 1 to 5, wherein a flow of the EGR gas discharged from the EGR gas passage is switched between an intake passage and an exhaust passage by a switching means. Gas reflux device. 7. An EGR gas discharged from an EGR gas passage by the EGR gas switching means when the internal combustion engine is cold.
The exhaust gas recirculation device for an internal combustion engine according to claim 6, wherein a part of the GR gas is introduced into the exhaust passage. 8. A thermostat provided in a cooling water passage through which the cooling water passes and controlling the flow of the cooling water in accordance with the temperature of the cooling water is provided, and the set temperature of the thermostat is set to the extent that the cylinder head is warmed by the EGR gas. The exhaust gas recirculation device for an internal combustion engine according to any one of claims 1 to 7, wherein the exhaust gas recirculation device is set low.